Energy dissipation in sheared granular flows

Using a two-dimensional discrete element computer simulation of a bounded, gravity-free Couette flow of particles, the heat dissipation rate per unit area is calculated as a function of position in the flow as well as overall solid fraction. The computation results compare favorable with the kinetic theory analysis for rough disks. The heat dissipation rate is also measure d for binary mixtures of particles for different small to large solid fract ion ratios, and for diameter ratios of ten, five, and two. The dissipation rates increase significantly with overall solid fraction as well as local s train rates and granular temperatures. The thermal energy equation is solve d for a Couette flow with one adiabatic wall and one at constant temperatur e. Solutions use the simulation measurements of the heat dissipation rate, solid fraction, and granular temperature to show that the thermodynamic tem perature increases with solid fraction and decreases with particle conducti vity. In mixtures, both the dissipation rate and the thermodynamic temperat ure increase with size ratio and with decreasing ratio of small to large pa rticles.